Cruel and Unusual

A rather bizarre article by Robert Weisberg, a professor of law at Stanford, in today's New York Times (registration required, I'm afraid). Writing on the US Supreme Court's ruling banning the executions of people who committed crimes as juveniles, Weisberg takes issue (siding with Justice Antonin Scalia) with the idea that a court can employ moral reasoning in order to make judgements. Weisberg writes that

This strategy provokes the (again perfectly reasonable) complaint that unelected jurists are now acting like pollsters, assessing the public's moral values. Or, worse, they are becoming arbiters of moral value themselves.

His implication is that the Supreme Court has no business engaging in "the cruel and unusual task of assessing America's evolving standards of decency."

This strikes me as being a little strange. The task at hand was to decide whether or not the execution of juveniles constituted a 'cruel and unusual punishment.' How, then, could a court not engage in moral reasoning over the question?

Weisberg's problem seems to be rooted in the fact that the majority justices made reference to international standards and other extra-constitutional sources in arriving at their ruling. But it's patently obvious that the US Constitution, that any constitution, cannot distinguish between acts that are cruel and unusual and those that are not.

Given this, if a Justice rules that act x is not cruel and unusual, he or she is still making a moral judgment. Or, if she or he claims that it is not their job to rule on such matters, then they are reneging on their obligation to interpret constitutional law. Whatever way you look at it, judgements without moral reasoning are impossible.

Or am I missing something?